The Production of Fuel Grade Butanol From Algal Carbohydrates Utilizing a Hybrid Biological and Chemical Process

Butanol has the potential to become a superior renewable fuel, either as a mixture with petroleum derived gasoline or as a stand-alone, neat fuel. The promise of butanol is currently marred by the relatively high cost of production. This paper explores a new and novel approach to the production of fuel grade butanol by combining a bacterial fermentation front end with a catalytic hydrogenation back end. Thus, the fermentation of algal carbohydrates to butyric acid includes a dialysis step to concentrate the butyric acid and remove the inhibitory organic acid from the fermentation broth. The concentrated and de-watered butyric acid is then converted to butanol in a liquid phase catalytic hydrotreater. The kinetics of the hydrogenation is discussed, and a discussion of the economics of the hybrid processing system is presented.